Solvent enhancement and isomeric effects on the NLO properties of a photoinduced cis-trans azomethine chromophore: A sequential MC/QM study

Abstract

This work uses a sequential Monte Carlo/Quantum Mechanics procedure to discuss how specific solute-solvent interactions and the photoinduced cis-trans isomerization affect the nonlinear optical (NLO) response of a recently synthesized azo-azomethine dye. The results show that the trans geometry increases the number of solvent molecules around the solute concerning the cis structure. Consequently, the trans isomer performed the major number of hydrogen-bonded structures with the solvent molecules. Considering the solvent contribution to the quantum mechanical properties, the results show that the solute polarization affects drastically all electronic properties drastically. For instance, concerning the vacuum conditions, the molecular dipole moment increases ca. 25% insolvent. Moreover, from vacuum to solvent, Density Functional Theory methods coupled to 6-311++G(d,p) basis set to show that the first and second-hyperpolarizability (β and γ) increase ca. 12% for the trans structure, indicating a high-power generation of second and third harmonic, which can be 580 times greater than that reported for urea (β=0.34×10-30 esu), which is a common NLO chromophore. Finally, the photo-induced cis-trans isomerization tunes the NLO response of the material from βcis=53.31×10-30 esu to βtrans=197×10-30 esu, which means an improvement of 270%.